"What are the German colors?" asked Ralph. [Illustration: _Allies' Distinguishing Mark_] "Black and white," said the corporal. "Oh, yes, they have a cross," said Alfred. "Yes; a cross in imitation of the iron cross, so far as its shape is concerned," he answered; "that is, a black cross on a white field." The company marched back to the line. During the next half hour there was nothing but expectancy, waiting, waiting,--that most trying thing for soldiers, who know that a battle is impending. Then a hundred feet to their rear there was a terrific explosion, which startled every one. This was followed by others, but none reached the trench line. Thus, during the whole day, there was an exchange of artillery, the greatest damage being done to those in the rear who were trying to get to the front. "With the long range guns the great danger isn't always with the fellows in front," said the corporal. [Illustration: _Black Cross on German Flyers_] At four that afternoon the company was startled by an order to leave the trenches and fall to the rear. Every one cast questioning glances, but the knapsacks and rolls were quickly seized, and within ten minutes they were in line with the regiments to the right and the left. There was no hurrying or disorder. "I wonder why we are going back?" asked Ralph. "I suppose it's our business to retreat," returned the corporal. They marched fully a mile to the rear, passing on the way at least half a dozen lines of trenches, which had been thrown up since the boys covered the ground the night before. Every trench line was filled with soldiers, those in the front being the first to retire. On the way they saw how the great shells had played havoc with many of the works. They again crossed the river, and at six o'clock that night a new line was formed, and the spades and picks were again brought into use. The booming of cannon was incessant, and, although they tried to get some sleep after midnight, they were frequently aroused by the marching of troops. At daylight they were again marched out of the trenches, and a quarter of a mile from the last trench halted to partake of breakfast. The march was directly south, and at noon they reached a town of some importance, called Chauny. They went through without halting, crossed the river Oise, and at four o'clock halted on the eastern banks of a stream, which flowed northwardly. Here they waited for orders. A picturesque bridge spanned the stream, and the boys wandered across. West of the river was a broad expanse of country, perfectly level, and thousands of people from the nearby villages lined the road, all crossing to the west.